A device of this type is known from DE 199 50 307 C1. For this known device, a feed head, which has the feed rollers that push the top sheet of the stack against an incline, lies on the stack of sheets to be separated. The leading edge of the top sheet runs up the incline and is thereby separated from the following, second sheet of the stack. The feed head is attached to the free end of a swiveling arm, so that it can follow the height of the stack. In order for the leading edge of the top sheet to be pushed up the incline, the leading edge must be bent upward at the level of the stack. This requires a bending length between the leading edge of the sheet and the action line of the feed rollers, which is dependent upon various factors. Such factors include, for example, the paper weight, the paper structure, the humidity, etc. The feed rollers adjust automatically to the required bending length by rolling away from the incline-and thus from the leading edge of the paper that is bearing against this incline-against the retractive force of a spring, until the leading edge is pushed up the incline. In the known device, the swiveling motion of the arm is blocked by the force of the retractile spring as soon as the feed rollers move away from the incline. The feed rollers are supported in a rocker, whose setting angle increases in the feed head when the feed rollers move away from the incline. This increases the pressure force, and thus the friction of the feed rollers in relation to the top sheet, in order to ensure a reliable feeding of the top sheet.
This known device has proved to be successful in practice. Since in this known device the force of the retractile spring blocks the swiveling motion of the arm, no initial tension may exist in the retractile spring in the inoperative position. The feed rollers must therefore maintain a certain minimum distance from the incline, so that the feed rollers bearing against the incline do not cause an initial tension that blocks the swiveling motion of the arm that affects the retractile spring. It is important for the reliability of the sheet-separation, however, that the distance between the leading edge of the top sheet bearing against the incline and the action line of the feed rollers on this sheet be as small as possible, particularly if the sheets have only slight bending stiffness.